Method of combatting the growth of undesired plants



8 Claims. (Cl. 71-94 ABSTRACT OF THE DISCLOSURE Use of N-substituted methyl-2,6-dichlorothiobenzamide as herbicidal agents. Examples are N-hydroxymethyl-2,6- dichlorothiobenzamide and .N-n-propoxymethyl-Z,6-dichlorothiobenzamide.

This invention relates to new and novel compounds particularly useful as herbicides.

This case is a division of my copending United States patent application Ser. No. 435,736, filed Feb. 26, 1965, said application Ser. No. 435,736 being a continuationin-part application of United States patent application Ser. No. 294,726, filed June 12, 1963, and now abancloned.

Many herbicidal compounds are known of varying effectiveness. One of the difficulties, however, with the practical use of most of the known herbicidal compounds lies in the fact that their herbicidal activities are not sufficiently specific. Thus in agricultural practice there are few herbicidal compounds that may be satisfactorily employed as most of the known herbicidal agents damage the desired crop to the same extent as they damage the undesired weeds.

A principal object of my invention therefore is to provide new and novel herbicidal compounds.

Another object of my invention is to provide new and novel herbicidal compounds that are selective in their herbicidal activities.

These and other objects of my invention will be ap parent from the description that follows:

According to my invention I have prepared novel halogenated thiobenzamide compounds of the formula:

United States Patent Patented Mar. 19, 1968 (2) represents a halogen atom,

B: group, may be prepared, for example, by causing a compound of the Formula 2 to react with an amine of the formula in which formula R and R represent an alkyl group having 1 to 5 carbon atoms or, together a saturated or unsaturated alkylene group having 4 to 5 carbon atoms.

In the case that R R and N together constitute a pyridine ring, the compounds of my invention can be prepared by causing a compound of Formula 2, in which Y is a halogen atom, preferably a chlorine atom, to react with pyridine.

The novel thiobenzamides of my invention wherein X is hydroxyl may be prepared by reacting a corresponding acid chloride with hexamethylene tetramine or by the simultaneous action of ammonia and formaldehyde or paraformaldehyde on a corresponding acid chloride. These novel compounds of my invention, however, (wherein X is hydroxyl) are preferably prepared by reacting a suitable dichlorothiobenzamide with formaldehyde or paraformaldehyde and especially with formalin.

The preparation and methods of employing the novel compounds of my invention will now be explained in greater detail with reference to the following examples:

EXAMPLE 1 3 ethereal solution was washed four times with 75 cc. of 2 N solution of caustic soda.

The collected caustic soda extracts were washed with 150 cc. of ether, after which the ether was removed by evaporation under reduced pressure at from 20 C. to 25 C. and the condensate was cooled to 10 C. After filtration, 200 cc. of concentrated hydrochloric acid were added while stirring. The resulting mixture was stirred for one hour at a temperature of from 15 to 20 C. and then allowed to stand. After standing 15 hours the precipitated oil had entirely solidified; the solid substance was drawn off, washed with water several times and dried. The yield of N-hydroxy-methyl-2,6-dichlorothiobenzamide was 163 g. (81% of the theoretical yield). Melting point 112 C.-115 C.

EXAMPLE 2 N-methoxymethyl-2,6-dichlr0thi0benzamide 5.08 grams of N-chloromethyl-2,6-dichlorothiobenzamide (prepared from N-hydroxymethyl-Z,6-dichlorothiobenzamide by means of PCl were suspended in 20 ml. of acetone.

3.6 grams of pulverized silver nitrate and 30 ml. of methanol were simultaneously added to this suspension within 5 to minutes while stirring, the temperature being maintained at 20-25 C. Then the mixture was stirred for another minutes and then poured on 2.1 g. of soda. The pH had become 7. The solvent was distilled off for the greater part. The residue was cooled to 0 C. and the crystallized substance was filtered off. The crystals were extracted with benzene. After the benzene solution had been evaporated to 5 ml., a solid was precipitated by adding petroleum ether. Yield 1.83 g. Melting range 133- 139 C. After one crystallization from isopropanol the melting range Was 142-144 C.

EXAMPLE 3 N-ethoxymethyl-2,6-dichlorothiobenzamide 1 18.0 g. of N-hydroxymethyl-2,6-dichlorothiobenzamide were mixed with 500 ml. of dry benzene. 66.0 g. of thionyl chloride were added dropwise while stirring within 15 minutes. The clear benzene solution was heated to boiling on the water bath for 15 minutes. After having cooled the reaction mixture to 10 C., 125 ml. of absolute ethanol were added in 5 minutes. Then stirring was continued at room temperature for another 30 minutes.

The solution was filtered, evaporated in vacuo to 200 ml. and replenished with another 200 m1. of benzene.

The mixture was extracted 3 times with 100 ml. of 2 N KOH after which the alkaline solution was acidified with concentrated hydrochloric acid, while cooling. The crystalline product formed was filtered off and dried in air. Yield 51 g. Melting point 114-115 C.

EXAMPLE 4 N m-propoxymethy l-2,6 -dichl0rothi0benzamide 14.2 g. of N-hydroxymethyl-2,6-dichlorothiobenzamide were mixed with 60 ml. of dry benzene. 5.1 ml. of thionyl chloride were added dropwise to this mixture in 5 minutes. The resulting solution was then boiled under reflux for '15 minutes, cooled to 10 C. and diluted with ml. of n-propanol. After 15 hours the solution was washed once with water and then 10 times with totally 500 ml. of 2 N potassium hydroxide solution. The extracts were combined, treated with carbon and carefully neutralized with concentrated hydrochloric acid while stirring and cooling in ice water. The precipitate was filtered off and crystallized from a mixture of 1 part of benzene and 2 parts of petroleum ether 40-60. Yield 2.5 g. Melting range 77-85 C. After recrystallization from ethanol/ water, 1:2. Melting point 88-9l C.

4 EXAMPLE 5 N -is0pr0-p0xymethy l-2,6 -dich lorothiobenzamid e 14.2 g. of N-hydroxymethyl-Z,6-dichlorothiobenzamide were mixed with 60' ml. of dry benzene. 5 .1 ml. of thionyl chloride were added dropwise to this mixture in 5 minutes. The resulting solution was boiled under reflux for 15 minutes, cooled to 10 C. and diluted with 20 ml. of isopropanol. After 15 hours the solution was washed once with water and then 5 times with 20 ml. of 2 N potassium hydroxide solution. The extracts were combined, treated with carbon and then carefully neutralized with concentrated hydrochloric acid while stirring and cooling in ice water. The precipitate was vacuum filtered off and crystallized from approximately 20 ml. of a mixture of 1 part of benzene and 2 parts of petroleum ether, 40-60. Yield 3.0 g. Melting range -122 C.

EXAMPLE 6 N-methoxymethyl-2,6-dichlorothiobenzamide 25 ml. of methanol in which 0.85 gr. of sodium had been dissolved, were added at 15-20 C., while stirring, within 20 minutes to a solution of 8.9 g. of N-chloromethyl-2,6-dichlorothiobenzamide in 30 ml. of acetone. After 75 minutes the reaction mixture was diluted with m1. of diethyl ether. The solution was washed with dilute acetic acid to weakly acid. Then the solution was extracted 5 times, each time with 20 ml. of 2 N sodium hydroxide. The combined alkaline extracts were purified with active carbon at room temperature. The mixture was filtered and the filtrate was carefully acidified with hydrochloric acid to pH 2 to 3 while cooling in an ice bath. The crystallized product was isolated and dried in air. Yield 0.93 g. Melting range 138-142 C.

EXAMPLE 7 N -(dimethylamin0methyl -2,6-dichlorothiobenzamide 20.6 g. of 2,6-dichlorothioobenzamide Were stirred at at temperature of 20 C. with a mixture of 20 ml. of 25% dimethylamine solution, 10 ml. of 40% formaline and 125 ml. of dioxane. After the mixture had been left to stand at 20 C. for 15 hours, it was poured into water. The resultant precipitate was filtered off and dried. Yield 25 g. Melting point 147-149" C.

EXAMPLE 8 N pyridiniummethyl -2,6-dichl0r0thi0benzamide chloride 23.6 g. of N-hydroxymethyl-2,6-dichlorothiobenzamide were mixed with 100 ml. of benzene. To this mixture there were added dropwise while stirring, and within 10 minutes, 13.5 g. of thionyl chloride. The benzene solution was heated on the water bath for 15 minutes. After the reaction mixture had been cooled to 10 C., 15 g. of pyridine were added.

The resulting precipitate was sucked off and dried in vacuo. Yield 30 g. Melting point -187 C.

The compounds according to the invention have a strong preemergence action on various Weeds. This action is shown in the following experiment in which seeds of various Weeds were sprayed with an aqueous solution or suspension of one of the compounds. After a few days the percentage of the seeds that had not germinated was determined. In Table I the results of an experiment are given in which the seeds were treated with a quantity of substance of the following formula, which, in practice, corresponds to 10 kg./ ha.

++ means 100% inhibition of the seed germination. means 80100% inhibition of the seed germination. :b means 10%'80% inhibition of the seed germination.

It has been found in post-emergence experiments that the compounds according to the invention also have an interesting action on young and fullgrown plants. With some compounds of my invention weeds in vegetation can be killed without the vegetation being damaged noteworthily.

The compound of Formula 1, in which X represents an isopropoxy group and n=0, has been found to be suitable for killing nettles in dwarf French bean.

The post-emergence action is shown in the following experiment in which various seeds and vegetation were sprayed with a solution or suspension of compounds of my invention in acetone in a quantity corresponding to 10 kg/ha. After some time the damage done to the plants was estimated and evaluated with a cipher from to 6, these ciphers having the following meanings:

0=no damage, 1=up to part of the leaves burned, 2= A part of the leaves burned, 3=% /s part of the leaves burned, 4= part of the leaves burned, 5 part of the leaves or more burned, 6=plant died.

(IJ1 lI ICHnX H TABLE II Dwarf Ohick- Ground X French Oat weed Nettle sel bean N(CH3)2 2 2 4 OCHa 0 2 2 002115 3 2 3 6 4 ()(OHz)2CHa 3 2 4 6 4 OCH(CH3)2 1 2 2 6 4 The compound N-hydroxymethyl-2,6-dichlorothiobenzamide was found to be particularly useful in that it was able to destroy dicotyledonous weeds in wheat and barley without harming these cereal crops. Thus this compound can be used in the early spring to act as a pre-emergent weed killer for winter wheat.

The production of a herbicidal composition in accordance with the invention may be effected in the manners known for such compositions. For example, an active substance may be mixed with a powdered inert carrier, such as chalk, dolomite, kaolin, china clay or attapulgite or dissolved or dispersed in an inert solvent, such as toluene, xylene, aliphatic, alicyclic or aromatic ketones, for example acetone, methylethyl ketone or cyclohexanone, or mixtures thereof with hydrocarbons, if desired with the addition of surface-active substances and dis- TABLE I White Annual Chick- Wild X mustard meadow weed Cress Millet oats grass (GHa)2 0 CH3 :l: 0 02 5 :l: 0 H2)2 Ha s)2 In this tablepersion agents. It may also be mixed with artificial manures.

Adust may be produced by mixing 5 parts by weight of an active ingredient with parts by weight of kieselguhr and grinding the mixture.

A wettable powder may be produced by intimately mixing 20 parts by weight of an active ingredient with 5 parts by weight of oleylamidomethyl taurate, 10 parts by weight of calcium lignin sulphonate and 65 parts by weight of chalk and grinding the resulting mixture.

Miscible oils containing from 5-30% and preferably from 10-20% of active ingredient and from 5-10% of ionogenic or non-ionogenic emulsifying agents or mixtures thereof may be produced by dissolving these ingredients in organic solvents, for example, aliphatic or aromatic ketones, such as acetone and cyclohexanone, if desired mixed with aromatic hydrocarbons, for example toluene and xylene.

A dispersion may be produced by pouring into water a miscible oil which, for example, is produced by mixing 25 parts by weight of active ingredient, 10 parts by weight of polyoxyethylene sorbitan fatty acid ester, 25 parts by weight of acetone and 30 parts by weight of methylethyl ketone.

While I have described my invention in connection with specific embodiments and applications, other modifications thereof will be readily apparent to those skilled in this art Without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. The method of combatting the growth of undesired plants comprising treating said undesired plants with a concentration of a compound of the formula:

wherein X is a member selected from the group consisting of hydroxy,

alkoxy of 1 to 5 carbon atoms, the group 6. The method of claim 1 wherein the compound is N-isopropoxymethyl-2,6-dichlorothiobenzamide.

7. The method of claim 1 wherein the compound is N- (dimethylaminomethyl -2, 6-dichlorothiobenzamide.

8. The method of claim 1 wherein the compound is N (pyridiniummethyl) 2,6 dichlorothiobenzamide chloride.

8 References Cited UNITED STATES PATENTS 3,187,042 1/1965 Richter 71-118 3,318,681 5/1967 Yates 7-98 JAMES O. THOMAS, 111., Primary Examiner. 

